Towards the resolution of the Microcotyle erythrini species complex: description of Microcotyle isyebi n. sp. (Monogenea, Microcotylidae) from Boops boops (Teleostei, Sparidae) off the Algerian coast

COI DNA barcoding is increasingly recognized as a significant new tool for the recognition and identification of animal species. Here, publicly available barcode data are compiled and analysed for birds (657 species) and fishes (1088 species). The proportion of species that cannot be barcode-distinguished by this marker is approximately 6.4% for birds and 2.1-2.5% for fishes. At all hierarchical taxonomic levels (species, genera, family, order, class), fish show greater mean COI divergence than birds. If two samples are barcode-identical, then for both birds and fishes, the probability that they are from the same species is 98-99%. The probability of conspecificity rapidly drops as divergence increases. At 2% COI divergence, this probability approximates to 1% for birds and 3% for fishes. The apparent difference between birds and fishes might partially reflect currently unrecognized cryptic species complexes in the latter. These probability estimates derive from pooled samples of birds and pooled samples of fishes, and will not apply in all situations. Recently evolved species complexes will have higher proportions of species that are barcode-identical. As barcode data accumulate, more refined statistical analyses will become possible. © 2009 Blackwell Publishing Ltd.

Members of the genus Schistosoma are generally grouped on the basis of egg morphology, intermediate host specificity, and geographic origin. We have tested hypotheses based on these groupings by phylogenetic analysis of nuclear ribosomal (ITS2) and mitochondrial (COI) nucleotide sequences. Both mitochondrial and nuclear DNA data strongly support "traditional" hypotheses that (a) members of the Schistosoma haematobium group form a monophyletic clade, (b) members of the S. mansoni group form a monophyletic clade, (c) S. japonicum and S. mekongi form a monophyletic group relative to other schistosomes, and (d) the African schistosomes form a clade to the exclusion of the two Asian species.

Partial nuclear 28S ribosomal RNA and mitochondrial cytochrome c oxidase subunit I (COI) gene sequences (953 and 385 nucleotides, respectively) of one fish monogenean (outgroup) and six polystome monogeneans (four Polystomoides spp. from the oral cavities and urinary bladders of freshwater turtles in Australia and Malaya, two Neopolystoma spp. from the urinary bladder and conjunctival sac of a freshwater turtle in Australia) were used to examine the question of whether congeneric species infecting different sites in the same host species have speciated in that host by adapting to different sites, or whether species infecting a particular site in one host have given rise to species infecting the same site in different hosts. Results show unequivocally that congeneric species infecting the same site, even of host species belonging to different suborders and occurring on different continents, are more closely related than congeneric species infecting different sites of the same host species. This is interpreted as meaning that speciation has not occurred in one host. Morphological evolution of polystomes has been very slow: few differences between species and even genera have evolved over a period of at least 150 Myr, and this is matched by low substitution rates of nucleotides, and the ambiguous position of species of different genera, depending on whether COI or 28S rDNA sequences are used.